Russian prime minister Dmitry Medvedev says he believes three members of punk band Pussy Riot should be freed from jail.

The women, who are due to appeal against their two-year jail sentences next month, were convicted of hooliganism after performing a protest song against Russian president Vladimir Putin in Moscow's main church.

The three women stormed the altar of Moscow's Christ the Saviour Cathedral in February, wearing bright-coloured balaclavas and clothes to belt out a "punk prayer" against Mr Putin.

The song included lyrics condemning the church's open support for the state and called on the Virgin Mary to "throw Putin out" of power.

Speaking at a meeting of ruling United Russia party officials, Mr Medvedev said extending the jailed Pussy Riot members' time in custody would be unproductive.

Mr Medvedev was harshly critical of the band's performance and said he was sickened by their actions.

But he said the six months the women had already served behind bars was sufficient.

There is speculation Mr Medvedev's comments may clear the way for the appeal court to order their release.